Digital holography with an internal impactor for particle imaging, classification, and mass density characterization

Abstract

A method and apparatus for monitoring particulate concentrations in ambient air use digital in-line holography and automated digital algorithms to classify and determine mass density and other characteristics of particles within a determined mass and size range. An embodiment provides a sampling plate on which particles are deposited at locations which depend on sizes and masses of the particles. A digital in-line hologram of the sampling plate is processed to obtain information about the particles. The method and apparatus have example application to environmental monitoring.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit under 35 U.S.C. § 119 of U.S. application No. 62 / 753,099 filed 31 Oct. 2018 and entitled DIGITAL HOLOGRAPHY WITH AN INTERNAL IMPACTOR FOR PARTICLE IMAGING, CLASSIFICATION, AND MASS DENSITY CHARACTERIZATION which is hereby incorporated herein by reference for all purposes.FIELD OF THE INVENTION[0002]The present invention relates generally to environmental monitoring systems and specifically to air monitoring systems which can perform real-time monitoring of particles in ambient air. Particle concentrations, mass density of particles, and / or other particle statistics may be monitored. Some embodiments provide portable hand-held particulate monitors.BACKGROUND OF THE INVENTION[0003]Rapid and accurate monitoring of particle size, particle distribution, and mass density of particles is important in many fields including aerosol science, the food industry, pharmaceutics, medicine, and environmental monitoring...

AI Technical Summary

Benefits of technology

The patent describes a device that captures particles based on their size and mass using a microsampling system. The device has a special nozzle designed to target specific particle sizes. The particles are captured based on their mass density and size, which allows for easy differentiation of similar particles. The device can process the captured images automatically, eliminating the need for manual intervention. The results can be displayed or printed, and statistical data on the size and mass of the captured particles can also be obtained. The technical effect of this device is a faster and more efficient method to capture and analyze particles, which can be useful in various fields such as air quality monitoring or material science research.

Problems solved by technology

While these devices offer high accuracy and high throughputs in particle measurements, they have many disadvantages including heavy weight, large size, high cost, and complicated maintenance.

Although they enable the sizing and counting of particles in real-time, such sensors suffer from many disadvantages.

One drawback is that such optical sensors are, inherently, unable to detect coincidence (i.e., when two particles are present in the sensing volume at the same time, the particles tend to be counted as one, possibly larger, particle).

This imposes a limit on the dynamic range of the particle measurement.

Therefore, accurate measurement of high concentrations of particles is a challenge for these devices.

This can cause severe errors in the conversion of the scattered light intensities into actual particle sizes.

Finally, none of these products offer a direct measure (i.e., a microscopic image of the captured particles).

Most currently available portable particle counters and sensors based on laser scattering are unable to measure the mass density of particles.

This approach, however, is labor-intensive and suffers from high overall cost.

Furthermore, since the sampling and inspection processes are separated (i.e., the sampling is performed in the field, whereas the sample analysis is conducted in a laboratory), this causes significant delays in the reporting of the results and limits its application for on-site monitoring.

Also, bench-top microscopes are cumbersome, heavy, and require specialized skills to operate.

Furthermore, the existing commercial particle sensors that are widely used in monitoring airborne particulates have many limitations when addressing food particles.

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